Year	Percent
1960	38.11659
1961	30.67815
1962	35.65574
1963	51.07004
1964	55.93525
1965	46.31849
1966	43.44194
1967	44.57187
1968	47.39369
1969	49.52919
1970	48.38373
1971	49.78764
1972	45.88595
1973	45.28524
1974	49.13333
1975	42.9943
1976	37.70651
1977	43.91758
1978	42.65167
1979	45.27105
1980	47.7788
1981	43.02215
1982	43.23183
1983	43.60884
1984	42.82915
1985	44.36005
1986	41.66381
1987	45.31805
1988	54.2958
1989	62.66962
1990	62.34343
1991	57.31146
1992	51.91765
1993	52.37755
1994	56.42119
1995	59.29121
1996	62.84806
1997	61.03999
1998	60.80445
1999	61.02266
2000	65.15852
2001	60.67383
2002	61.48472
2003	59.8672
2004	53.81476
2005	53.13035
2006	49.90532
2007	49.03975
2008	57.14081
2009	49.50732
2010	57.83776
2011	62.84121
2012	60.47538
2013	59.05728
2014	52.57031
2015	49.92787
2016	26.40726